The present invention relates to an apparatus and method for tensioning, stretching, or pulling a sheet-like, or web of, material widthwise and more particularly for tensioning, stretching, or pulling a single layer of sheet-like material, or multiple layers of sheet-like materials, to remove wrinkles, ripples and the like from the material.
Certain types of sheet-like, or webs of, material, such as fabrics, felts, and the like, are processed on needling looms, finishing machines, or other processing equipment to obtain a finished product. At first, the work piece may consist of an unprocessed single layer of material. The work piece also may consist of several layers of material or a laminate. The word "laminate" as used herein should be construed in its broadest sense. That is, the word "laminate" includes a plurality of overlying layers either joined together, or not joined together. The term "web of material" as used herein, in a general sense, refers to either a single layer of material or a laminate.
In a typical setup, a single layer of material, or a laminate, is loaded onto a material-processing machine. The processing of the sheet-like material may include interweaving or needling layers of batt onto it. The processing also may include passing the web of material through a finishing machine.
In certain situations, it may be more desirable to manufacture laminates, instead of a single layer of material. One reason for this is that laminates maintain consistent physical characteristics from product to product. Each layer of a laminate may be constructed differently or may be made of different materials altogether. Often, these multi-layered webs include at least one, and often two or more layers of base material, such as fabric, and layers of batt, which are subsequently interwoven onto the base layers.
As the material is being loaded onto the machine or as the material moves in the machine direction on the machine, one or more of the layers may develop wrinkles, ripples or other non-conformities. One reason for these problems is that the layers are stretched in the machine direction (MD) to pull the circumferences of the layers as close to one another as possible. The machine direction, or MD as used herein, refers to the longitudinal direction that the material travels when moving on a material-processing machine. This pulling in the MD direction causes a change in the material's cross machine direction (CMD) dimension. The cross machine direction or CMD as used herein refers to the lateral direction, which is substantially perpendicular to the machine direction (MD).
This relationship between the pulling in the MD and the shrinkage in the CMD dimension is called the material's contraction ratio. In some instances, the layers are constructed differently. Thus, each layer may have its own contraction ratio. As a result, differential width reductions in neighboring fabrics will result in wrinkles, ripples, and the like, in the layers of material. A single layer may wrinkle, as well, due to the pulling in the MD and the subsequent reduction of the CMD dimension of the single layer.
These non-uniformities typically present significant problems, especially prior to, and/or during, a needling, finishing, or other process. That is, if wrinkles in the layers are processed into the material (e.g., needled in via the needling loom or finished in via the finishing machine), non-uniformities develop in the finished product and the material must be reworked or, worse yet, scrapped altogether. Both of these options prove to be inefficient and costly due to added labor costs, production line shut downs and the need for additional raw materials. On the other hand, if wrinkles, ripples, or other non-uniformities are removed before further processing, they usually do not reappear after the single layer or laminate has been needled, finished or otherwise processed. Thus, there is a need to remove wrinkles from a single layer of material, or from a laminate, prior to further processing on a material-processing machine.
Conventional ways to remove these wrinkles, ripples, and the like, have included manual labor. Typically, at least two, and sometimes as many as six machine operators, are necessary to pull at the lateral sides of a single layer or a laminate to create a sufficient CMD tension. This manual process is extremely costly in terms of the amount of labor hours required to perform a given tensioning session. Also, this manual process is very difficult to repeat with consistent results, due to natural human error. Consistency, however, is important in this type of industry.
Attempts have been made to automate the tensioning or pulling of a web of material in general and specifically in the CMD or widthwise direction. For example, U.S. Pat. No. 3,822,448 to Cho provides an apparatus that includes a pair of rotary discs disposed at opposite side edges of a traveling fabric and a pair of push plates adapted adjacent the rotary discs. The pair of push plates is moved toward or away from the rotary discs in opposing relation thereto for spreading the fabric web widthwise. This apparatus also includes guide rollers positioned ahead of the spreading units to guide the fabric at each edge. These types of spreading apparatus are relatively complicated. They include machine parts, having their own relative motion, that need to interact at precise moments in order to achieve their objective of spreading a web of material. These types of apparatus also require a drive motor to actuate, for instance, the rotary discs. Such drive motors may need to be controlled, maintained, and repaired. In addition, since these types of apparatus are separately driven, and have their own relative motion vis-a-vis the motion of the web, they require extra energy to run. They also may, on occasion, have to be regulated to make sure the relative motions are in synchronization with the traveling web of material. Finally, these types of apparatus appear to only address the spreading of a single layer of material.